A medical endoscope for observing a body cavity of a patient is known. A flexible tube that is an essential part of an insert section of an endoscope is constructed of a flexible tube structure around which a jacket is formed. This jacket is formed with a thermoplastic layer such as a urethane polymer layer applied to a circumferential surface of the flexible tube structure, and a top coat layer applied to the thermoplastic layer. The flexible tube structure includes a spiral tube and a tube-like mesh. The spiral tube is made of a metal band wound in a helical fashion, and the tube-like mesh wraps around the spiral tube.
The flexible tube is frequently bent or twisted during operation, and then cleaned, sterilized and disinfected after every use. Such handling causes abrasion and scratches on the jacket, which may be developed into a damaged area such as a hollow.
A repairing method in which plasma is irradiated to a damaged area of a flexible tube is known (see Japanese Patent Laid-Open Publication No. 2006-218107). This plasma irradiation removes deposits from a surface of the damaged area, and makes reactive groups project from the surface and roughens the surface so as to improve adhesion between the damaged area and the repair material applied thereto. In addition, a repairing method to put a flexible tube in an infrared heating element is known (see U.S. Patent Application Publication No. 2005/0203337 A1 corresponding to Japanese Patent Laid-Open Publication No. 2005-253950). In this method, after polymer as a repair material is applied to a damaged area, the flexible tube is put in the infrared heating element to dry and harden the repair material.
In the methods described in the above publications, No. 2006-218107 and No. 2005/0203337 A1, the repair material may be projected like edges from the surface of the top coat layer and hardened, resulting in surface irregularities of the top coat layer. After the endoscope is cleaned, disinfected and sterilized, the surface of the repaired endoscope is wiped with alcohol-soaked gauze repeatedly. During the wiping, the gauze may be snagged on the edges. A force to pull the snagged gauze may cause the repair material to peel off. This may mislead a cleaning operator to think of the repaired area as a defect.